Electric lamp

ABSTRACT

A lamp in which the reflector which is provided with a halogen incandescent lamp is beaded, on its widened circumference, around the edge of a cover glass and an epoxy glue is present between said flanged part and a more central part of the cover glass. The flanged edge serves to secure the cover glass and the epoxy resin serves for a substantially completely diffusion-tight seal against water vapour from the atmosphere.

United States Patent 1191 a Boekkooi et al. [4 1 Jan. 8, 1974 {541 ELECTRIC LAMP 1,339,695 5 1920 Douglas 240/415 3,010,045 11/1961 Pl t 240 41 SB X 1 lnvemorsl Anion Bmkkml; Andreas Marla 1,322,044 11/1919 2 40/4155 Heeman, both of Emmasmgel, 1,622,437 3/1927 Freund.. 240/4155 Netherlands 2,317,035 4/1943 Dana 240/4l SB X [73] Assignee: U.S. Philips Corporation, New

York Primary Examiner-Fred L. Braun [22] Filed: Sept. 13, 1972 Attorney-Frank R. Trifari [21] Appl. No.: 288,596

[30] Foreign Application Priority Data [57] ABSTRACT Sept. 17, 1971 Netherlands 71 12768 A lamp in which the fl t which is provided with a halogen incandescent lamp is beaded, on its widened [52] US. CL, 240/415, 240/41 SB Circumference around the edge f a cover glass andv 1 C'- .7 v i an epoxy glue is present between said flanged part and of Search n SB, a more central part of the cover 'glass The flanged 240/41 B, 41.5, 41.55, 41.6, 93, 151 edge serves to secure the cover glass and the epoxy resin serves for a substantially completely diffusionl l References Cited I tight seal against water vapour from the atmosphere.

UNITED STATES PATENTS 2,003,687 6/1935 Graham 240/415 4 Claims, 1 Drawing Figure ELECTRIC LAMP The invention relates to an electric lamp in which at least one incandescent lamp is arranged inside a gastight envelope consisting of a metal reflector and a cover glass, the reflector comprising a supporting edge for enclosing the cover glass, a glued joint being present between the cover glass and the supporting edge of the reflector. Such an electric lamp is known.

In the known lamp which is used as a vehicle head light and in which the incandescent lamp arranged in the reflector is a halogen incandesent lamp, the cover glass is secured to the reflector by a glued joint. Said glued joint serves on the one hand to transmit mechanical forces between the reflector and the cover glass, while on the other hand it should readily seal. The difference between the coefficient of expansion of the metal reflector and the cover glass which nearly always consists of compressed glass, requires a flexible type of glue.

This type of joints has been found to work loose rather easily when the joint is exposed to great thermal load under strongly varying atmospheric conditions, for example, when a halogen incandescent lamp is used as a light source. This is undesirable, also in connection with traffic safety.

it has furthermore been found that the cover glass formed from compressed glass is not entirely smooth over its side which faces the reflector and with which it engages the reflector edge. As a result of this, taken over the circumference of the cover glass, the distance between the cover glass and the said reflector edge between which the glued joint is present, may vary from zero to, for example, 0.4 mm. As a result of this, water vapour may diffuse through the layer of glue into the reflector space and condense on the inside of the reflector which in a mounted lamp will rather rapidly give rise to corrosion of the reflecting layer present on the inner wall of the reflector.

It is the object of the invention to provide a lamp construction in which the joint between the reflector and the cover glass is very rigid and diffusion-tight to a considerable extent.

The lamp according to the invention is characterized in that the supporting edge for enclosing the reflector is curled around the circumferential edge of the cover glass, preferably by a flanging operation, and the glued joint is present between the flanged edge where it is in contact with the cover glass and a circumferential part of the cover glass situated more towards the axis of the reflector. In this construction the cover glass engages the supporting edge of the reflector in a tightly fitting manner throughout its circumference without the interposition of glue in spite of the fact that cover glasses of compressed glass are used which do not have entirely smooth engaging sides. By introducing a suitable type of glue, preferably an epoxy resin, into the annular space between the curled reflector edge and a part of the reflector situated more towards the reflector axis a solid glued joint is obtained which is hardly exposed or is not exposed to mechanical loads. The diffusion tightness against water vapour of said layer of glue is then great. Since in this manner an annular channel is present on the side of the cover glass remote from the reflector between the curled edge of the reflector and the cover glass, the introduction of epoxy glue which is used in a thin liquid condition is rather simple. For this purpose it is sufficient to arrange the reflector with its cover glass directed upwards and to pour the glue into the channel. This presents the possibility of accurately dosing and using only a small quantity of epoxy resin which is cost-saving.

In the lamp according to the invention the possible diffusion of water vapour through the glued joint is so small that by means of a suitable drier for example molecular sieves, the water vapour pressure can be maintained so low that condensation of water vapour does not occur for a very long time, for example a few years. According to an embodiment a lamp thus constructed is characterized in that a drier is present in the space between the curled edge of the reflector and the circumferential edge of the cover glass, above which the water vapour pressure at the highest operating temperature which can occur in said space is smaller than or corresponds approximately to the water pressure at 0C.

The drawing shows diagrammatically a so-called halogen sealed beam lamp. This lamp comprises a metal reflector 1 which is provided on its inner surface with a reflecting layer of aluminium, a transparent cover glass 3 of compressed glass and a halogen incandescent lamp 5 the conductors 7 and 9 of which are connected to the terminals 13 and 11 ofa base 15. Said base is connected to the reflector 1 by means of a cold setting epoxy resin.

The reflector 1 comprises a supporting edge which has a flange 21 extending transverse to the reflector axis 19 and on which the cover glass 3 supports while enclosing a ring 17 of cardboard. The said flange 21 comprises a cylindrical part 23 of which a portion 25 is curled by a flanging operation, The curled portion 25 is provided so that the cover glass 3 at its flanged part 27 is clamped between the flange 21 and the free edge 29 of the flanged portion 25. The edge 29 is in contact with said flange 27 throughout the circumference of the flange 27.

An annular space which is filled with a mass 33 formed from a cold-setting epoxy resin is present between the portion 25 and a cylindrical wall 31 of the cover glass 1 directed more towards the reflector axis 19. Said mass which is processed in a thin liquid state is provided in a position of the lamp in which the reflector axis 19 and the space between the edge 25 and the wall 31 are directed upwards as a channel to receive said mass. The quantity of glue can be accurately dosed. Also by this manner of enclosing the mass of glue it is achieved that the diffusion for water vapour from the atmosphere through said mass and taken from the reflector axis 19 to the edge 29 becomes smaller and smaller.

In the torus-shaped space 35 which is formed as a result of the flanging operation and which during operation of the lamp forms the relatively coldest place, a drier is present. As a result of this it is possible, in the case of any diffusion of water vapour, to keep the lamp internally dry for a very long time, for example a few years. As driers are preferably used so-called molecular sieves of which synthetic zeolites which are marketed by Union Carbide are examples.

What is claimed is:

1. In an electric lamp of the type having at least one incandescent lamp arranged inside a gas-tight envelope and consisting of a metal reflector and a cover glass, the improvement comprising that the cover glass has a circumferential outer lip, said lip having an inner annular face for abutting the reflector, an outer circumferential edge portion and an outer annular face, said outer face forming a space having an L-shaped crosssection with a cylindrical wall of the cover glass, the reflector having a central axis and having a portion for supporting the cover glass, said supporting portion of the reflector extending over the outer lip of the cover glass and substantially conforming to the inner abutting face and outer edge and having a portion curled over the lip toward the axis of the reflector, the curled portion having a free end pressing against the outer face of the lip, the lower portion of the curl including the free end forming an openended annular volume with said L-shaped portion, said annular volume having an epoxy resin disposed therein to join the glass and reflector portions.

2. An electric lamp as claimed in claim 1 wherein a drier is present in the space within the curled portion of the reflector and bounded by the outer face of the lip, above which the water vapour pressure at the highest operating temperature which can occur in said space is smaller than or corresponds approximately to the water pressured at 0C.

3. An electric lamp as claimed in claim 2 wherein said drier is comprised of molecular sieves.

4. The lamp of claim 1 wherein an annular ring of cardboard is disposed between the inner abutting face and the reflector. 

1. In an electric lamp of the type having at least one incandescent lamp arranged inside a gas-tight envelope and consisting of a metal reflector and a cover glass, the improvement comprising that the cover glass has a circumferential outer lip, said lip having an inner annular Face for abutting the reflector, an outer circumferential edge portion and an outer annular face, said outer face forming a space having an L-shaped cross-section with a cylindrical wall of the cover glass, the reflector having a central axis and having a portion for supporting the cover glass, said supporting portion of the reflector extending over the outer lip of the cover glass and substantially conforming to the inner abutting face and outer edge and having a portion curled over the lip toward the axis of the reflector, the curled portion having a free end pressing against the outer face of the lip, the lower portion of the curl including the free end forming an openended annular volume with said L-shaped portion, said annular volume having an epoxy resin disposed therein to join the glass and reflector portions.
 2. An electric lamp as claimed in claim 1 wherein a drier is present in the space within the curled portion of the reflector and bounded by the outer face of the lip, above which the water vapour pressure at the highest operating temperature which can occur in said space is smaller than or corresponds approximately to the water pressured at 0*C.
 3. An electric lamp as claimed in claim 2 wherein said drier is comprised of molecular sieves.
 4. The lamp of claim 1 wherein an annular ring of cardboard is disposed between the inner abutting face and the reflector. 